1. Field of the Invention
The present invention relates to cutting saws, and more particularly, to a saw tooth insert and the means for mounting it to a saw.
2. Description of the Prior Art
It is now common to use circular saws on feller heads, for severing the trunk of a tree to be felled. Since the circular saw is made to rotate in a horizontal plane near the ground, when the feller head is in an operative position, it is not surprising that the teeth inserts on the periphery of the circular saw may be subject to severe shocks. In such situations, it is desirable to minimize the damage to the circular saw. It would be preferable to contain the damage to one tooth or only a few teeth which could then be easily replaced.
Most prior art circular saws include a circular disc with radial inserts mounted in gullets cut out in the discs. Thus, in the event that a tooth bit should strike an immovable object, such as a boulder, it is conceivable that the tooth and bit would be destroyed with the possibility of damage to the disc as well. The loads would, in most cases, be transmitted through the tooth shank sitting radially in the gullet, and thus to the disc. It is evident that such loads would be applied tangentially to the saw disc against the radially extending shanks. C-shaped teeth would also be faced with similar stresses causing probable damage to the disc.
U.S. Pat. No. 4,932,447, Morin, issued June 12, 1990, describes a circular saw having a square frusto-pyramidal head with a shank received in a holder in the form of a circular cylindrical tube welded to the periphery of the saw disc and a pin passing transversely through the holder and the shank to hold the tooth against rotation. The cutting edges and tips are formed by forming a concave spherical recess at the base of the pyramid. As set out in the patent, a feature is the possibility of rotating the tooth on its axis to present new pairs of tips and new cutting edges at the exterior when the tips and edges previously located at the cutting edge have lost their sharpness or have been damaged. There are some disadvantages to a square tooth. For instance, as admitted in the patent, the tips must be rounded in order to prevent breakage. On a square tooth, the tip is formed at the intersection of two walls at 90.degree. and the spherical recess. This configuration makes for a very sharp tip, and one that is susceptible to breakage. The tooth as described in Morin includes a shank in a holder with a pin passing through the shank. Such an arrangement weakens the construction thereof. The circular saw in the feller environment is made to rotate in the 1000 r.p.m. range. Any sudden impact on the teeth, in the Morin construction, may cause a tooth to be dislodged. Given the high degree of centrifugal forces acting on the teeth, damage or injury might be caused if a tooth should break off.